Synthesis and characterization of solvated lanthanide(II) bis(triisopropylsilyl)phosphide complexes

Lanthanide (Ln) silylamide chemistry is well-developed, but the corresponding silylphosphide chemistry is immature; there are only ten structurally characterized examples of Ln(II) bis(trimethylsilyl)phosphide complexes to date, and no reported derivatives with bulkier R-groups. Here we report the synthesis of the first f-block bis(triisopropylsilyl)phosphide complexes, [Ln{P(SiⁱPr₃)₂}₂(THF)_x] (1-Ln; Ln = Sm, Eu, x = 3; Ln = Yb, x = 2), by the respective salt metathesis reactions of parent [LnI₂(THF)₂] with 2 eq. of [Na{P(SiⁱPr₃)₂}]_n in toluene. Complexes 1-Ln were characterized by a combination of NMR, EPR, ATR-IR, electronic absorption and emission spectroscopies, elemental analysis, SQUID magnetometry and single crystal X-ray diffraction. These data contrast with those obtained for related Ln(II) bis(trimethylsilyl)phosphide complexes due to the bulkier ligands in 1-Ln, and also with Ln(II) bis(triisopropylsilyl)amide complexes due to a combination of longer Ln–P vs. Ln–N bonds and the softer nature of P- vs. N-donor ligands.